1. Field of the Invention
The invention is directed to determining which tools or toolset have the greatest impact on manufacturing line performance and more particularly to a method for determining the performance components of a manufacturing line.
2. Description of the Related Art
Over the past two decades continuous flow manufacturing (CFM) has been the principle operational tool to help manage and improve the utilization of manufacturing assets. As the name connotes, the key focus of CFM is to measure and manage the throughput of tools/toolsets that comprise the manufacturing line. To this end, there have been a variety of systems proposed to help manage throughput with their attendant control methodologies.
Semiconductor manufacturing is faced with significant investment and cost challenges. The investment required to build and tool a semiconductor manufacturing line has steadily increased so that now in excess of $1 Billion is needed. In addition, the industry has been characterized by products (e.g., dynamic random access memories "DRAMS") that have sustained long term price declines of some 27% per year over the past 20 years. A significant component of maintaining this price decline has been the ability of manufacturing/engineering to reduce costs by increasing productivity, not only in terms of good chips per wafer, which are driven by technology and yields, but by identifying and improving the utilization of the installed tool base.
One of the principle methods used to improve asset utilization in manufacturing has been continuous flow manufacturing (CFM) which includes a number of techniques that focus primarily on the flow of product through the line as the means to identify and fix problems in the line. One such example is the Theory of Constraints, which determines the toolset(s) which limit the throughput of the line and then provides a set of operational roles (Drum-Buffer-Rope) that seek to maximize the use of the constraining toolset(s). Another example, that was developed by the Japanese as part of their lean manufacturing, is the use of KANBANS, which are devices for limiting the movement of product between toolsets. The result is a limit on the amount of work in progress (WIP) in front of each toolset. Ideally, a KANBAN ensures that there is neither to much nor too little WIP; too much WIP results in line congestion while too little WIP allows a toolset to run out of work.
In the past few years there has been an increased awareness in semiconductor manufacturing that there is a relationship between the utilization of effective capacity and cycle time and the invention presents a new methodology to analyze this relationship and produce unexpected benefits when compared to conventional methods and structures.